Aseptic meningitis

Most patients who have aseptic meningitis can be cared for on an outpatient basis. In some cases, patients with severe headache, nausea, vomiting, or CSF pleocytosis with a polymorphonuclear leukocyte predominance can be admitted for observation.

No specific treatment exists for most of the viruses that cause meningitis; therefore, management, for the most part, is supportive and includes analgesics, anti-nausea medications, intravenous

fluids, and prevention and treatment of complications. Patients who are elderly,  immunocompromised, or have received antibiotics prior to presentation may be considered for empiric therapy for 48 hours, even if viral meningitis is the suspected diagnosis. Otherwise, the clinician can consider observing the patient without antibiotic therapy. If aseptic meningitis due to HSV is suspected (eg, concomitant genital lesions), empiric therapy with Acyclovir (10 mg/kg intravenously every eight hours ) can be considered for hospitalized patients.

When it is not clear whether the patient has a viral or bacterial process, empiric antibiotics may be given after obtaining blood and CSF cultures or observation with repeat lumbar puncture in 6 to 24

hours. If the patient is symptomatically improved and culture results are negative, then antibiotics can generally be stopped without a repeat LP. Repeat LPs may be indicated in patients with persistent symptoms who do not have a clear diagnosis.

Bacterial meningitis

Bacterial meningitis is a medical emergency, and immediate steps must be taken to establish the specific cause and initiate effective therapy. The mortality rate of untreated disease approaches 100

percent, and, even with optimal therapy, there is a high failure rate. 

Antimicrobial therapy, along with adjunctive dexamethasone when indicated, should be initiated as quickly as possible after the performance of the lumbar puncture (LP) or, if a computed tomography (CT) scan of the head is to be performed before LP, as quickly as possible after blood cultures are obtained.

Because of the general limitation in antimicrobial penetration into the CSF, all patients should be treated with intravenous antimicrobial agents. Oral antimicrobial agents should be avoided since the

dose and tissue concentrations tend to be considerably lower than with parenteral agents. An exception can be made for rifampin, which is useful as a synergistic agent for treatment of meningitis caused by beta-lactam–resistant Streptococcus pneumoniae or coagulase-negative Staphylococcus.

Early intravenous administration of glucocorticoids (usually dexamethasone) has been evaluated as adjunctive therapy in an attempt to diminish the rate of  hearing loss, other neurologic complications, and mortality. Based upon clinical trial data from Europe, the main indication for dexamethasone therapy in adults is known or suspected pneumococcal meningitis. Since the etiology of bacterial meningitis is not usually known at the time of treatment initiation, dexamethasone is administered to patients in the developed world with suspected bacterial meningitis in whom the organism is unknown. Dexamethasone should only be continued if the CSF Gram stain and/or the CSF or blood cultures reveal S. pneumoniae.

Supportive care

Careful management of fluid and electrolyte balance is important, since both over- and under- hydration are associated with adverse outcomes.

Patients with bacterial meningitis may have increased intracranial pressure (ICP). Patients who are comatose may benefit from an ICP monitoring device. Methods to reduce ICP include elevating the head of the bed to 30º and hyperventilation to maintain PaCO2 between 27 and 30 mmHg. Another method that has been evaluated for reducing ICP is oral administration of the hyperosmolar agent glycerol. A randomized trial in adults with bacterial meningitis in Malawi was stopped early however, because planned interim analysis demonstrated increased mortality by day 40 in the glycerol group (63 versus 49 percent). The reason for this finding is unclear but might relate to an increased incidence of seizures in the patients who received glycerol. Another possible reason could be a rebound increase in ICP as the drug is eliminated, although ICP was not monitored in this trial. In contrast with this trial involving adults, some studies using glycerol have shown promising results in children with bacterial meningitis, although further data are needed before it can be recommended.

There is limited evidence for the effect of hypothermia treatment in patients suffering bacterial meningitis. In a study of therapeutic hypothermia in adults with community-acquired bacterial meningitis, the incidence of hospital mortality (20 versus 49 percent) and adverse neurologic outcome (ie, a Glasgow outcome score 1 to 3; 44 versus 66 percent) were significantly lower in patients treated with therapeutic hypothermia. However, the number of enrolled patients was

small, and outcomes in this study of the 41 enrolled patients were compared with historical controls.

Although not routinely recommended, there are settings in which repeat LP may be performed:

- When there is no improvement by 48 hours after initiation of appropriate therapy

- Two to three days after the initiation of therapy of meningitis due to micro-organisms resistant to standard antimicrobial agents, especially for those who have also received adjunctive dexamethasone therapy and are not responding as expected, or for infection caused by a

gram-negative bacillus, which is much more common with healthcare-associated infection.

- Persistent fever for more than eight days without another explanation

Repeat CSF cultures should be sterile. For patients in whom repeat cultures are positive despite appropriate therapy with parenteral antibiotic therapy, administration of intrathecal (or intraventricular) antibiotics may be considered.